This invention relates to the field of non-woven textile materials and articles made therefrom.
Current non-woven textile technology consists of dry and wet processing varied to control the properties of the end product. Wool felts cannot be made by dry processes if the felting properties of wool are to be used. Needled felts are limited in their hardness, rigidity and other properties, unless chemical and/or wet processes are added, for example through the use of impregnants. The continued development of new types of synthetic fibers has increased the range of properties of synthetic fiber needled felts, resulting in the displacement of wool felts from many areas of use. Among these areas are: marking pen nibs or tips, resin bonded filters, plate and frame filter sheets, marking stamp pad reservoirs and battery separator media.
Prior art for the modification of these and other types of non-woven textile materials has included the post-manufacture treatment of the textile with a variety of chemical materials, such as lattices, resins, plastics and the like, and has included also laminations, coatings and mechanical finishes. Marking pen nib felts are normally treated with formulations of melamine-formaldehyde to enhance rigidity and wear resistance, while retaining the ability to allow ink to flow freely through the fiber interstices. Phenolic complex resins continue to be used to produce rigid fibrous filter cartridges capable of withstanding pressures exceeding 100 psi. Plate and frame cloths have been coated with various resins (viz., acrylic, urethane, etc.) to provide a clean cake release from the surface. Stamp pad felts have been treated with wetting agents to promote ink leveling, and have been laminated to inert materials to provide rigidity and reduce cost. Battery separators have been produced which accommodate the special chemical requirements associated with advanced battery technology.
In general, these modifications have required wet processing and the use of chemical materials which are increasingly becoming categorized as hazardous or unsafe. Therefore, increased environmental concerns have vastly reduced the range of materials which can safely be used to modify the basic fibrous structures of non-woven textiles.
Within the last decade, certain specialty synthetic fibers identified generically as "bicomponent" or "bico" fibers have been produced. In general, these consist of, but are not limited to, two varieties of a single polymer type. Structurally, they consist of a core polymer and a sheath polymer. Creation of these new fibers has permitted the redevelopment of some products formerly requiring the post-treatment of basic non-woven structures, through a re-alignment of customary manufacturing techniques, adapted to the use of these fibers. Because the core and sheath polymers are often varieties of the same polymer, they retain their polymeric identity, but have different melting points. This feature permits their use as bonding agents. While bondable fibers have existed for a considerable period of time, their melting points rendered them unusable for many purposes, or their chemical properties excluded them from important uses.
A non-woven melded fabric, known under the trademark "Cambrelle" is composed of bico fibers. Upon heating to the melting point of the sheath polymer, the fibers soften and unite to form a fabric, which is used for carpet backing, road reinforcement, upholstery, interlinings, tablecloths and other household applications.